The present invention relates to a process for preparing mono-alkylated aromatic compounds by subjecting an aromatic hydrocarbon to alkylation with a C.sub.2 to C.sub.4 olefin or transalkylation with a polyalkyl aromatic hydrocarbon, under at least partial liquid phase conditions, utilizing zeolite beta as the alkylation/transalkylation catalyst.
Most industrial processes for the alkylation and/or transalkylation of aromatic hydrocarbons employ a Friedel-Crafts type of catalyst such as aluminum chloride, boron trifluoride, hydrofluoric acid, liquid and solid phosphoric acid, sulfuric acid and the like. These materials are highly corrosive to process equipment, cause many operational problems, and are often difficult to dispose of in an environmentally acceptable manner.
It has long been a goal of research to find noncorrosive, solid catalysts to replace the Friedel-Crafts catalysts. To this end, various types of zeolite catalysts have been proposed.
U.S. Pat. No. 2,904,607 shows the alkylation of aromatic hydrocarbons in the presence of a crystalline metallic aluminosilicate having a uniform pore opening of 6 to 15.ANG. units. Sodium and magnesium aluminosilicates are cited as examples.
U.S. Pat. No. 3,251,897 describes a process wherein the alkylation reaction is carried out at a temperature not more than 600.degree. F., preferably under substantially liquid phase conditions. The catalysts for this process are crystalline aluminosilicates (i.e., zeolites), which contain hydrogen and/or a rare earth element and which have a uniform pore size of at least 6.ANG.. The rare earth and hydrogen forms of zeolite types X, Y, and mordenite are specifically disclosed.
U.S. Pat. No. 3,385,906 describes a process for transalkylating benzene and diisopropylbenzene to make cumene in the presence of a zeolite molecular sieve catalyst wherein not more than 90% of aluminum atoms in the zeolite are associated with monovalent cations.
U.S. Pat. No. 3,631,120 describes an alkylation process wherein the zeolite catalyst has a silica-to-alumina ratio from about 4.0 to about 4.9 and is activated by ammonium exchange followed by calcination.
U.S. Pat. No. 3,641,177 describes an alkylation process wherein the zeolite component of the catalyst has undergone a series of ammonium exchange, calcination, and steam treatments. The catalyst employed in the examples would be described now as an "ultrastable" or "steam stabilized" Y zeolite.
U.S. Pat. Nos. 3,769,360, 3,776,971, 3,778,415, 3,843,739, and 4,459,426 relate to methods for combining alkylation and transalkylation to obtain improved yields of monoalkylated aromatics. Rare earth exchanged Y (RE-Y) and steam stabilized Y zeolites are cited in these patents as being particularly effective catalysts.
European Patent Application No. 7,126 shows the advantages of zeolite omega for alkylating benzene with propylene to make cumene. Compared to zeolites RE-Y, L, and steam stabilized Y, only zeolite omega was able to meet cumene purity specifications while achieving a run length of 500 hours.
European Patent Application No. 30,084 shows the alkylation of benzene with dodecene over zeolites ZSM-4, beta, ZSM-20, Linde Type L, ZSM-38 and RE-Y.
U.S. Pat. Nos. 3,751,504 and 3,751,506 show transalkylation and alkylation in the vapor phase over ZSM-5 type zeolite catalysts. ZSM-5 is a medium pore size zeolite having an effective pore size between 5 and 6.ANG..
U.S. Pat. No. 4,049,737 relates to the selective propylation of toluene to make cymene over ZSM-5.
Alkylation or transalkylation over other medium pore size ZSM-type zeolites is taught in U.S. Pat. Nos. 4,016,245 (ZSM-35), 4,046,859 (ZSM-21), 4,070,407 (ZSM-35 and ZSM-38), 4,076,842 (ZSM-23), 4,291,185 (ZSM-12), 4,387,259 (ZSM-12), 4,547,605 (ZSM-23).
Despite the available literature on zeolite catalysis and the recognized advantages of replacing the Friedel-Crafts catalysts with a noncorrosive catalyst, zeolites have not yet found widespread use in industrial alkylation processes. Under commercially realistic conditions, the zeolite catalysts described in the literature have tended to deactivate rapidly due to fouling, produced the desired product in a lower yield than the competing Friedel-Crafts catalyst, or made a product which failed to meet established purity specifications. The one notable exception is the use of a ZSM-5 type catalyst for the vapor phase alkylation of benzene with ethylene to make ethylbenzene.